The photopolymerization and characterization of methyl methacrylate initiated by nanosized titanium dioxide

Polymerizations of methyl methacrylate initiated by nano-TiO2 semiconductors were studied in this paper. The heterogeneous polymerizations were carried out by dispersing the TiO2 particles into MMA aqueous solutions. UV light at 365 nm was employed to stimulate photocatalysis of the TiO2 particles. The progress of the polymerizations was investigated and the products were characterized using various tools of instrumental analysis such as NMR, TGA, DSC, and FT-Raman spectroscopy. The nature of free radical mechanism of the polymerization was confirmed. It was found that the polymerization is of a double-species initiation. Both the valence-band hole and the OH-radical work as initiators. The results from thermal analysis show that the TiO2 particles, remained in the raw products, significantly improve the thermal stability of the PMMA polymers. It is well interpreted in terms of initiation mechanism via the valence-band holes.